Towards the end of the episode, when Scotty Valens is interrogating the person who played Sally Bowles on the stage version of Cabaret within the episode, the actress's hands alternate from being on/next to her face (when the camera is facing her) to being on the table (when the camera is facing Valens) between shots.
The company is rehearsing the song "Maybe This Time," but it was not in the stage version of Cabaret. It was added for Liza Minelli to sing in the film version, which came later, and would not have been included in the performance rights for the stage version.